1. Field of the Invention
This invention relates generally to injection molding. In particular, this invention relates to so-called “quick-change” devices facilitating removal and installation of mold sub-assemblies from and into an injection molding machine.
2. Description of Related Art
It is known to provide two-part frame constructions for installation in the clamp unit of an injection molding machine wherein the two-part frame facilitates removal and installation of mold insert members of components of a mold assembly from and into the clamp unit (so-called “quick change” frame constructions). Such two-part frames comprise an ejector part adapted to receive an ejector “side” of a mold sub-assembly comprising members for forcibly separating molded articles from a mold member and an injection part adapted to receive an injection “side” of a mold sub-assembly comprising members for admitting material to cavities formed by mating mold members. The ejector part of the frame is mounted and attached to a movable platen comprising the clamp unit and the injection part of the frame is mounted and attached to a fixed platen comprising the clamp unit. Relative movement of the movable and fixed platens is effective to abut and separate mold members having article forming surfaces establishing the size and shape of articles to be molded. When abutted, the article forming surfaces of such mold members define at least one so-called “mold cavity”. The two-part frame construction comprises elements for seating and clamping the “sides” of a mold sub-assembly that are effective to reduce the time required to remove and install the mold sub-assembly from and into the machine clamp unit that would otherwise be required. To remove a mold sub-assembly, the ejection and injection parts of the frame are positioned so that the “sides” of the mold sub-assembly abut one another, the “sides” of the mold sub-assembly are clamped to each other and the two “sides” are removed from the frame as a unit. To install a mold sub-assembly, the two-parts of the frame are positioned to accommodate therebetween two “sides” of the mold sub-assembly clamped abuttingly to one another, the two sides are inserted into the frame as a unit, clamps holding the two “sides” of the mold sub-assembly together are released, the ejection “side” of the mold sub-assembly is clamped to the ejector part of the frame and the injection side of the mold sub-assembly is clamped to the injection part of the frame.
As known from U.S. Pat. No. 6,802,704 (hereinafter “U.S. Pat. No. 6,802,704”), a clamping device is advantageously used to selectably clamp parts of the frame together and to clamp the injection part of the frame to a so-called “hot half” of a mold assembly. The clamp construction of U.S. Pat. No. 6,802,704 is directed to allowing use of a two-part frame as known in the art with mold assemblies comprising a sub-assembly for distributing material from an injection unit to cavities of a mold sub-assembly and comprising nozzles that project through the injection part of the frame and into the injection “side” of the mold sub-assembly. The clamp construction of U.S. Pat. No. 6,802,704 allows the two-parts of the frame to remain joined as the movable platen is moved away from the fixed platen a sufficient distance to provide clearance between the injection part of the frame and the projecting nozzles of the material distributing sub-assembly. Once clear of the projecting nozzles, a mold sub-assembly can be removed from the frame. As illustrated in U.S. Pat. No. 6,802,704 the two-part frame is retracted a distance that allows the injection part of the frame to remain supported by pins projecting from that part of the frame into the material distributing sub-assembly. The arrangement of support pins as illustrated imposes a limit on the distance “X” by which the injection part of the frame can be separated from the material distributing sub-assembly and maintain support by the illustrated support pins.
It is known that accurate alignment of nozzles of material distributing sub-assemblies with mold insert members in which the nozzles are received is required to achieve sealing between the nozzles and other components of a mold assembly to prevent leakage of material under normal operating conditions. However, while quick change frame constructions are effective to reduce time required for installation of mold assemblies in clamp units, the known constructions do not include means for achieving accurate alignment of nozzles with mold insert members. Hence, in view of limitations of known quick change constructions, there is a need for improved two-part frame constructions overcoming limitations on the extent of permitted separation between an injection part and a material distributing sub-assembly and deficiencies for effecting alignment of nozzles of material distributing sub-assemblies with mold insert members.